1. Field of the Invention
This invention relates to clay filled blends and more specifically, it relates to clay filled blends of ethylene/vinyl ester copolymers modified with processing oil.
2. Description of the Prior Art
Use of fillers in compounding of adhesives, coatings, mastics, etc. is old art. Generally, the use of fillers contributes stiffness and resistance to elevated temperatures for blends. In addition, fillers increase the density of the blend; and, because most fillers are far less costly than resinous binders, the final filled blends are significantly less costly than are the unfilled precursors.
Clay is a useful filler for many resin-based blends because it is low in cost and can readily be blended in conventional equipment. However, blends which contain both ethylene/vinyl acetate (EVA) copolymer and clay at elevated temperatures often rapidly decompose and liberate copious quantities of anhydrous acetic acid (HAc).
Schwartz U.S. Pat. No. 3,904,456 is related to a method for inhibiting transmission of airborne noise by interposing in the air space between the noise source and the location to be insulated a thin, dense normally self-supporting film or sheet composed essentially of from about 10 to about 40% by weight of ethylene/vinyl acetate copolymer having an average vinyl acetate content of from about 10 to about 42% by weight and a glass transition temperature of at least about 30.degree. C. below the average ambient temperature in the air space, and from about 60 to about 90% by weight of inorganic filler materials, such as sulfates, carbonates, oxides, etc. of barium, calcium, cadmium, etc., effective to produce an overall density greater than at least 2 grams per cubic centimeter.
EVA copolymers have been used industrially for nearly two decades, however, they are not known to be used in conjunction with processing oils as articles of commerce. This could well be an outgrowth of the way EVA commercialization has proceeded. That is, most EVA blends are based on EVA/paraffin wax technology, where paraffin wax weight is often up to ten times the weight of the EVA present. Furthermore, despite the obvious savings inherent in using lower-cost, lower-quality waxes, such as scale wax or slack wax, all attempts to do this have failed. The reason was always the same--the oil content of the wax migrated and destroyed the effectiveness of the coating or adhesive when the oil reached the bond or sheet surface. Thus, compounders "knew" that oil could not be used in EVA blends and technology developed along other lines.
Rundle U.S. Pat. No. 3,497,375 discloses coating compositions for wooden concrete molds consisting of ethylene/vinyl acetate copolymer and paraffinic oil. There is no filler employed in the coating compositions of this patent.
Monaghan U.S. Pat. No. 3,379,193 discloses teeth covers made of ethylene-vinyl acetate copolymer in itself or in combination with mineral oil and, if desired, with fibers and coloring materials. The preferred formulation is disclosed to be 47% by weight of ethylene-vinyl acetate copolymer, 47% by weight of mineral oil, 5% by weight of nylon fibers, and 1% by weight of titanium dioxide.
German Patent Application No. 2,319,431 discloses sound deadening composites suitable for use in automobiles which consist of a highly filled polymer sheet (for example, 300-1200 or even up to 1500 parts of filler per 100 parts of polymer) which on its backside is provided with a filler material sheet, e.g., a polymer foam. Suitable polymers for use are disclosed to be terpolymers of ethylene, propylene and a non-conjugated diene (EPDM), polyvinyl chloride (PVC), mixed polymers of ethylene and vinyl acetate (EVA), styrene-butadiene mixed polymers (SBR) and mixtures of these materials with thermoplastic polymers, such as polystyrene and polyolefins.
Boyer U.S. Pat. No. 3,010,899 discloses blends of ethylene/vinyl acetate resin and mineral oil which are either rubbery or grease like depending upon the proportion of oil to resin and can be used as a substitute for crepe rubber or as a grease. It is further disclosed that fillers such as carbon black or finely divided clays can be added to the rubbery products to increase hardness and produce materials suitable as floor tile. As indicated for example in claim 11, the filler, carbon black, is present in a "minor amount" while the oil-ethylene/vinyl acetate copolymer mixture is present in a "major amount". In Example 2 an oil+resin/carbon black ratio of 4 parts by weight to 1 part by weight is indicated.
Rosenfelder U.S. Pat. No. 3,203,921 discloses the use of compositions consisting essentially of 73-88% by weight of a homo- or copolymer of ethylene (which can be ethylene/vinyl acetate or ethylene/ethyl acrylate copolymer), 2-7% by weight of an aliphatic paraffinic hydrocarbon mineral oil and 10-20% by weight of a mineral filler, (for example, calcium carbonate, barium sulfate, etc.) for preparing blow-molded objects such as dolls.